Electrical auxiliary module for a vehicle steering system

Abstract

An auxiliary module has a gearbox, a motor, a torque detector and a controller. The gearbox has a casing, a sun gear, a planet gear assembly, a driven gear and a driving axle. The planet gear assembly engages the sun gear and has a driving gear, multiple planet gears and an annular gear. The planet gears are mounted rotatably on the driving gear and engage the sun gear. The annular gear is mounted around and engages the planet gears. The driven gear engages the driving gear. The driving axle is mounted co-axially on the driving gear. The motor is connected co-axially to the sun gear. The torque detector is mounted on the casing of the gearbox with fasteners to detect torque applied on the driving axle. The controller is connected electrically to the motor and the torque detector to adjust torque output from the motor.

What is claimed is: 
     
       1. An electrical auxiliary module for a vehicle steering system comprising:
 a gearbox having
 a casing; 
 a sun gear mounted rotatably in the casing; 
 a planet gear assembly mounted in the casing, engaging the sun gear and having
 a driving gear having a center and multiple through holes defined through the driving gear and arranged in a circle about the center of the driving gear; 
 multiple planet gears rotatably mounted on and attached to a side surface of the driving gear with axles and engaging the sun gear, wherein the axles are respectively mounted in the through holes in the driving gear and respectively mounted through the planet gears, and the driving gear serves as a planet carrier for the planet gears; 
 an annular gear mounted around and engaging the planet gears; 
 
 a driven gear mounted rotatably in the casing and engaging the driving gear; and 
 a driving axle mounted co-axially on the driven gear and having two ends extending out from the casing; 
 
 a motor mounted on the casing of the gearbox with fasteners and connected co-axially to the sun gear; 
 a torque detector mounted on the casing of the gearbox with fasteners and mounted around the driving axle to detect torque applied on the driving axle; and 
 a controller connected electrically to the motor and the torque detector to adjust torque output from the motor according to the torque detected by the torque detector, wherein 
 the controller comprises
 a controlling unit connected electrically to the motor and the torque detector to change torque provided by and rotating speeds of a rotating shaft of the motor; 
 a detecting unit connected electrically to the controlling unit for detecting multiple vehicle statuses and sending detected signals to the controlling unit; and 
 a vehicle speed detecting interface electrically connected to the controlling unit for detecting vehicle speed and sending detected result to the controlling unit; and 
 
 a gear ratio relationship between the sun gear and the planet gear assembly of the gearbox is shown as following equation:
   φ 1 +( N   3-1 ×φ 3 )−( N   3-1 +1)φ 2 =0
 
     N   3-1   =T   3   /T   1    
 Wherein, φ 1  is an angular speed of the sun gear, φ 3  is an angular speed of the annular gear, N 3-1  is a gear ratio of the sun gear and the annular gear, T 1  is tooth number of the sun gear, T 3  is tooth number of the annular gear and φ 2  is the output angular speed.